From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 174B8C001DE for ; Mon, 31 Jul 2023 05:36:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229675AbjGaFgo (ORCPT ); Mon, 31 Jul 2023 01:36:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54438 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229613AbjGaFgo (ORCPT ); Mon, 31 Jul 2023 01:36:44 -0400 Received: from mail-pf1-x42e.google.com (mail-pf1-x42e.google.com [IPv6:2607:f8b0:4864:20::42e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 131FAE68; Sun, 30 Jul 2023 22:36:43 -0700 (PDT) Received: by mail-pf1-x42e.google.com with SMTP id d2e1a72fcca58-68336d06620so4150680b3a.1; Sun, 30 Jul 2023 22:36:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1690781802; x=1691386602; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=GEYDHdxW+GqO/A72zpM2Ivj3ad0HfR7AVeRSROhpavA=; b=hDTr062anlw+gU4Ml5fkr/Wqeg81olwlqGYFQzMcGd2un12W9W64LQ7TevFxj5f1Jm 8o9JeYLduBM6K5Hs9Fj7tuqmRpQGaYtGr6HDisLzsMgBiLSA86A9ZmktUufhCxB2hKOs GWvdcmnVbpg7aBq4MFXNyMoigFMjx3JzHoDa9Qca6zbR/hnQAFtGcQgqHWfIE/7tI0RW Fe8z8zsvcNZsoNlq8LgtwJDeO+aOdsuM6dZGpYPPw7KZxhf/nFap6vsmRp6mgb/byoib yYlVAuMo8XAOylVDtFebP2AI0Z/lrKaAKBLd8rsdmkOVvROvRAlmmhJMWKD8SB325F4i UB9Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1690781802; x=1691386602; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=GEYDHdxW+GqO/A72zpM2Ivj3ad0HfR7AVeRSROhpavA=; b=gZXBsfdv0hXqWl+gwnCAWU2G2w9mpD+ikB26owqVqoCHyzgggPzYB0ruOVk3fNP6wS 8cFw3J6Yd3Tl8S1+zzDGaxtGlnSYsiKx3XfVSNjQzMzhQEXkDeq76wZalT67vL1i0dLl 8o/HtQ7Yg4xp7Xlf5FzrJ8cdrYLLQom6mpwjEyapWwFN6MVn/YJcPQz86KIa04bQw0BR 6IjTOnmpYTv76DhibA1+58WttNMnQ/ZpvKkKkmetkFqsy4dBJBlgwxT8DW2sf/pHEYt5 MEDNB5tK4smSegFtoJBggmZTdsiUSMqHoR74To2QQi17jjPlxrILyvm8V/LuUNceoQIk jQEQ== X-Gm-Message-State: ABy/qLbAjvTcLh2rS4h0XH4CyJqxEqkiEPUroAhaeBFADLCXd+2Qx83z eeLrl9Q+DkTtER1JePNKkAg= X-Google-Smtp-Source: APBJJlE3/PWrxtTzXeEVgTjilO2kKRi76gBdRfysdoM8scgKejMgaNyfKWfKEnHr4SYWD58E0UkGlg== X-Received: by 2002:a05:6a20:8f19:b0:13b:c4a8:1a68 with SMTP id b25-20020a056a208f1900b0013bc4a81a68mr9762941pzk.34.1690781802268; Sun, 30 Jul 2023 22:36:42 -0700 (PDT) Received: from google.com ([2620:15c:9d:2:6d25:c0f1:d8d5:201c]) by smtp.gmail.com with ESMTPSA id e26-20020aa78c5a000000b0064d57ecaa1dsm4052358pfd.28.2023.07.30.22.36.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 30 Jul 2023 22:36:41 -0700 (PDT) Date: Sun, 30 Jul 2023 22:36:38 -0700 From: Dmitry Torokhov To: Marek Vasut Cc: Jeff LaBundy , linux-input@vger.kernel.org, Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= , Frieder Schrempf , Manuel Traut , Thierry Reding , linux-pwm@vger.kernel.org, alsa-devel@alsa-project.org, Jaroslav Kysela , Takashi Iwai Subject: Re: [PATCH] Input: pwm-beeper - Support volume setting via sysfs Message-ID: References: <20230512185551.183049-1-marex@denx.de> <0ef98ec1-6191-c72e-2362-310db7f09b84@denx.de> <06379f26-ab24-85f9-783f-0c49d4291b23@denx.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <06379f26-ab24-85f9-783f-0c49d4291b23@denx.de> Precedence: bulk List-ID: X-Mailing-List: linux-pwm@vger.kernel.org On Sat, May 13, 2023 at 11:02:30PM +0200, Marek Vasut wrote: > On 5/13/23 03:51, Marek Vasut wrote: > > On 5/13/23 03:12, Jeff LaBundy wrote: > > > Hi Marek, > > > > Hi, > > > > > On Fri, May 12, 2023 at 08:55:51PM +0200, Marek Vasut wrote: > > > > The PWM beeper volume can be controlled by adjusting the PWM duty cycle, > > > > expose volume setting via sysfs, so users can make the beeper quieter. > > > > This patch adds sysfs attribute 'volume' in range 0..50000, i.e. from 0 > > > > to 50% in 1/1000th of percent steps, this resolution should be > > > > sufficient. > > > > > > > > The reason for 50000 cap on volume or PWM duty cycle is because > > > > duty cycle > > > > above 50% again reduces the loudness, the PWM wave form is inverted wave > > > > form of the one for duty cycle below 50% and the beeper gets quieter the > > > > closer the setting is to 100% . Hence, 50% cap where the wave > > > > form yields > > > > the loudest result. > > > > > > > > Signed-off-by: Marek Vasut > > > > --- > > > > An alternative option would be to extend the userspace input > > > > ABI, e.g. by > > > > using SND_TONE top 16bits to encode the duty cycle in 0..50000 > > > > range, and > > > > bottom 16bit to encode the existing frequency in Hz . Since frequency in > > > > Hz is likely to be below some 25 kHz for audible bell, this fits > > > > in 16bits > > > > just fine. Thoughts ? > > > > --- > > > > > > Thanks for the patch; this seems like a useful feature. > > > > > > My first thought is that 50000 seems like an oddly specific limit to > > > impose > > > upon user space. Ideally, user space need not even care that the > > > beeper is > > > implemented via PWM and why 50000 is significant. > > > > > > Instead, what about accepting 0..255 as the LED subsystem does for > > > brightness, > > > then map these values to 0..50000 internally? In fact, the leds-pwm > > > driver > > > does something similar. > > > > The pwm_set_relative_duty_cycle() function can map whatever range to > > whatever other range of the PWM already, so that's not an issues here. > > It seems to me the 0..127 or 0..255 range is a bit too limiting . I > > think even for the LEDs the reason for that limit is legacy design, but > > here I might be wrong. > > > > > I'm also curious as to whether this function should be a rogue sysfs > > > control > > > limited to this driver, or a generic operation in input. For > > > example, input > > > already allows user space to specify the magnitude of an FF effect; > > > perhaps > > > something similar is warranted here? > > > > See the "An alternative ..." part above, I was wondering about this too, > > whether this can be added into the input ABI, but I am somewhat > > reluctant to fiddle with the ABI. > > Thinking about this further, we could try and add some > > EV_SND SND_TONE_WITH_VOLUME > > to avoid overloading EV_SND SND_TONE , and at the same time allow the user > to set both frequency and volume for the tone without any race condition > between the two. > > The EV_SND SND_TONE_WITH_VOLUME would still take one 32bit parameter, except > this time the parameter 16 LSbits would be the frequency and 16 MSbits would > be the volume. > > But again, here I would like input from the maintainers. Beeper was supposed to be an extremely simple device with minimal controls. I wonder if there is need for volume controls, etc, etc are we not better moving it over to the sound subsystem. We already have: sound/drivers/pcsp/pcsp.c and sound/pci/hda/hda_beep.c there, can we have other "advanced" beepers there as well? Adding sound maintainers to CC... Thanks. -- Dmitry